Houses and buildings with crawl space type spaces are typically provided with vents in the exposed foundation wall around the crawl space to prevent moisture build-up and damage. These crawl space or “foundation” vents are cemented or otherwise permanently secured in openings left in the block or cement wall at the time of construction, the openings in the wall providing for a flow of air to and from the crawl space. The vents typically have a grille and/or screen or mesh face to keep rodents and insects out, and often have closeable louvers or dampers to seasonally adjust airflow in colder climates.
Theoretically, the closeable-type vents are left open in warmer weather to keep the crawl space vented and dry, and in colder climates closed for the fall/winter to keep the crawl space (and the floor of the house) warm. However, the adjustment mechanisms in these vents are often relatively complex and prone to damage or failure through abuse such as being painted over, banged with lawn equipment, and exposed to the elements. The vents can accordingly become difficult to adjust properly and can even get stuck in one position. Over time the damage and wear accumulate, making the original unattractive and ripe for replacement. However, calling a contractor in for the relatively minor but time-consuming task of replacing one or more original, cemented-in vents can be inordinately expensive.
Since the vents are cemented or otherwise permanently secured in the foundation wall around the perimeter of the crawl space (often a considerable distance from the crawl space access in the house or building), it can be a cold, dirty crawl to try to repair, close, seal, and sometimes even insulate the vents from the inside. Accordingly, one can often see plastic sheeting, insulation boards and hay bales mounted and piled at unsightly intervals around the foundations of houses with crawl spaces in colder climates as homeowners try to slow down the wasteful, expensive, and uncomfortable heat loss from their homes via the crawl space vents, and to reduce the corresponding potential for frozen pipes. U.S. Pat. No. 6,149,514 attempts to partially solve the problem with a cut-to-size, snap-on, insulated cover, with snap-fittings secured to the foundation wall around the cemented-in vent to receive the insulated cover.
Another disadvantage of conventional closeable crawl space vents is the relatively limited ventilation area they offer for a given size when maximum venting is desired, since the louvers and associated support and adjustment structure reduce the net venting area of the screen or mesh and obstruct airflow.